Summary:
This is a professional unit that allows you to carry multiple tools on your truck in a cost-effice and space consious manner.
You may need to carry several tools (ie: line trimmer and steel head trimmer (saves time in chaning heads)).
Good tools to carry on truck may be two trimmers, edger, hedge trimmer and possibly a pole pruner (depending on type of work you do).
This is designed for the professional, and is going to set you back a few dollars, but worth it for what you get in engine size and overall benefit.

Strengths:
Great value for the tool.
Reliable.
No apparently weakness found in the connection joint, which was initial fear.
Lots of available tools to add on.
You can build the tools over time, and not have significant capital outlay to add additional tools.
If you have several of these, it is easy to work around if one is down for a day for service - lots of flexibility.
Takes up less room on truck than each unit having engine of its own.
Less servicing and lower cost.

Weaknesses:
One may need to carry a couple of power heads if they send out three man crews, therefore overall savings may not be as great as initiall expected.
Perhaps a bit more fuel used at times for the smaller tools, vs having smaller dedicated unit to do the job.
If one units fails you may loose all tools (unless you have several of these in your fleet)